The study of genetic interaction networks that respond to changing conditions is an emerging research problem. Bandyopadhyay et al. (2010) proposed a technique to construct a differential network (dE-MAPnetwork) from two static gene interaction networks in order to map the interaction differences between them under environment or condition change (e.g., DNA-damaging agent). This differential network is then manually analyzed to conclude that DNA repair is differentially effected by the condition change. Unfortunately, manual construction of differential functional summary from a dE-MAP network that summarizes all pertinent functional responses is time-consuming, laborious and error-prone, impeding large-scale analysis on it. DiffNet is a novel data-driven algorithm that leverages Gene Ontology (GO) annotations to automatically summarize a dE-MAP network to obtain a high-level map of functional responses due to condition change.